Interference cancellation within wireless transceivers

Abstract

The receiver includes a Rake receiver for separating a received signal into multipath components, an interference selector for selecting interference symbols corresponding to interfering paths and subchannels, a synthesizer for synthesizing an interference signal from selected paths and estimated subchannel symbols, and a canceller for constructing a projection operator or a scale-invariant subtraction operator to cancel selected interference in multipath components of the received signal, or from the received signal itself. The interference canceller may use a sequence of symbol estimates to simultaneously cancel inter-channel interference and inter-symbol interference. Interference cancellers may be placed at one or more locations within the receiver chain.

We claim: 
     
       1. A CDMA receiver, comprising
 a baseband front-end configured to perform baseband processing on a received baseband signal, 
 a descrambler located downstream from the baseband front-end, 
 a despreader located downstream from the descrambler, 
 an interference selector configured to select at least one interfering symbol from at least one of the descrambler and the despreader for producing at least one selected interference symbol, 
 a synthesizer coupled to the interference selector and configured to synthesize an interference signal from the at least one selected interference symbol, 
 a channel emulator configured for imparting at least one channel distortion to the at least one interference signal, and 
 a canceller located downstream from at least one of the baseband front-end, the descrambler, and the despreader. 
 
     
     
       2. The receiver recited in  claim 1  wherein the channel emulator is configured to identify multipath components in the received baseband signal. 
     
     
       3. The receiver recited in  claim 1 , wherein the canceller is configured to process a sequence or a filtered sequence of estimated symbols. 
     
     
       4. The receiver recited in  claim 1 , wherein the canceller is configured to perform at least one of an orthogonal projection, an oblique projection, and a scale-invariant subtraction. 
     
     
       5. The receiver recited in  claim 1 , wherein the canceller is configured to produce soft-decision estimates of one or more transmitted signals. 
     
     
       6. The receiver recited in  claim 1  configured to operate in at least one of a base station and a handset. 
     
     
       7. The receiver recited in  claim 1  integrated in a chipset. 
     
     
       8. A CDMA reception method, comprising
 providing for baseband front-end processing of a received baseband signal for producing a digitized received baseband signal, 
 providing for descrambling the digitized received baseband signal for producing a descrambled baseband signal, 
 providing for despreading the descrambled baseband signal for producing a despread baseband signal, 
 providing for selecting at least one interfering symbol from at least one of the descrambled baseband signal and the despread baseband signal for producing at least one selected interference symbol, 
 providing for synthesizing an interference signal from the at least one selected interference symbol, 
 providing for imparting at least one channel distortion to the at least one interference signal, and 
 providing for cancellation located downstream from at least the baseband front-end processing. 
 
     
     
       9. The reception method recited in  claim 8 , wherein providing for cancellation is configured to process a sequence or a filtered sequence of estimated symbols. 
     
     
       10. The reception method recited in  claim 8 , further comprising providing for physical channel estimation to identify multipath components in the received baseband signal. 
     
     
       11. The reception method recited in  claim 8 , further comprising providing for producing soft-decision estimates of one or more transmitted signals. 
     
     
       12. The reception method recited in  claim 8 , wherein providing for cancellation further includes performing at least one of an orthogonal projection, an oblique projection, and a scale-invariant subtraction. 
     
     
       13. A chipset configured to perform the reception method recited in  claim 8 . 
     
     
       14. A digital computer system programmed to perform the method recited in  claim 8 . 
     
     
       15. A computer-readable medium storing a computer program implementing the method of  claim 8 . 
     
     
       16. A CDMA receiver, comprising
 means for baseband front-end processing of a received baseband signal for producing a digitized received baseband signal, 
 means for descrambling the digitized received baseband signal for producing a descrambled baseband signal, 
 means for despreading the descrambled baseband signal for producing a despread baseband signal, 
 means for selecting at least one interfering symbol from at least one of the descrambled baseband signal and the despread baseband signal for producing at least one selected interference symbol, 
 means for synthesizing an interference signal from the at least one selected interference symbol, 
 means for imparting at least one channel distortion to the at least one interference signal, and 
 means for cancellation located downstream from at least the baseband front-end processing. 
 
     
     
       17. The CDMA receiver recited in  claim 16 , wherein the means for cancellation is configured to process a sequence or a filtered sequence of estimated symbols. 
     
     
       18. The CDMA receiver recited in  claim 16 , further comprising means for physical channel estimation to identify multipath components in the received baseband signal. 
     
     
       19. The CDMA receiver recited in  claim 16 , further comprising means for producing soft-decision estimates of one or more transmitted signals. 
     
     
       20. The CDMA receiver recited in  claim 16 , wherein the means for cancellation further includes means for performing at least one of an orthogonal projection, an oblique projection, and a scale-invariant subtraction. 
     
     
       21. The CDMA receiver recited in  claim 16 , including at least one of handset, a base station, and a chipset.